1. Field
The present disclosure relates to display modules, and more particularly, to reducing yellowing of an image in a display module.
2. Description of the Related Art
Generally, a display panel such as a liquid crystal display panel is a passive display device that displays an image not by self-emitting light but by receiving external light.
In order for a liquid crystal display panel to be a self-emissive display, since a liquid crystal display module itself is not self-emissive, a back light unit is installed on a rear surface of the liquid crystal display panel to emit light. Accordingly, an image may be observed even in a dark place. The back light unit is used for a surface light source element, such as a light element for a light up sign, in addition to a passive display module, such as a liquid crystal display panel.
The backlight unit is classified as a direct light type or as an edge light type according to a position of a light source element. The direct light type backlight unit has a structure in which a plurality of light source elements disposed directly under a panel directly emit light on the panel. The edge light type backlight unit has a structure in which a plurality of light source elements disposed at a side of a light guide panel emit light and the emitted light is transmitted to a display panel through the light guide panel.
A light source element may be any of a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a light emitting diode (LED), etc. The CCFL has a structure in which electrodes of both ends of a fluorescent lamp are formed inside a tube. The EEFL has a structure in which electrodes of both ends of a fluorescent lamp are formed outside of a tube. The LED has advantages, such as a compact size, low power consumption, and high reliability, and thus has been widely used as a light source element of a display module.
Recent passive display modules become thinner and larger, and a light guide panel manufactured to meet these trends has different characteristics. For example, in a light guide, yellowing of an image color gets worse at an area away from a portion on which light is incident. In particular, if a light guide panel is manufactured using an injection molding method, discoloration of a material of the light guide panel due to heat generated when manufacturing the light guide panel cannot be prevented, and if this discoloration is too intense, it is perceivable by the naked eye and thus product quality is deteriorated.